I am not a lawyer so, while I have this question, I cannot answer it.
My question is simple: Is Scientology’s Contract for Services a valid, legal and enforceable contract?
Certainly, the Church of Scientology’s stable of expensive lawyers would, and do, insist it is fully enforceable — but is it?
I looked at several legal-advice websites. This one has the following criteria for whether a contract is valid:
Identify an offer, acceptance, and consideration. For a contract to be valid, it must have these three basic elements: a specific offer, [3] acceptance of the terms of the offer,[4] and consideration, which is the agreed-upon exchange of goods or services. [5]
– A valid offer must be sufficiently definite.[6] It must be clear, unequivocal, and direct.
…
– A contract must contain consideration: mutual promises to do something or to refrain from something that a party has a legal right to do. Without this mutual promise, there is no valid consideration and the contract is illusory.
Does the Scientology Contract for Services fulfill these criteria?
To be clear, what “specific offer” is the church offering? What “clear, unequivocal and direct” offer does the Church of Scientology propose?
Absolutely nothing.
Very specifically and explicitly the Church of Scientology promises to deliver … absolutely nothing, ever.
Neither the Church nor any other Scientology church or organization makes any claim … that any particular result may be forthcoming from my participation.
Church of Scientology Contract for Services
And what “consideration” does the church demand from the Scientologist? In exchange for this explicit “nothing”, the church requires Scientologists give up every single legal right they would have to protect themselves. These rights are extremely valuable.
… I am forever abandoning, surrendering, waiving, and relinquishing my right to sue, or otherwise seek legal recourse with respect to any dispute, claim or controversy against the Church, all other Scientology churches, all other organizations which espouse, present, propagate or practice the Scientology religion, and all persons employed by any such entity both in their personal and any official or representational capacities, regardless of the nature of the dispute, claim or controversy.
Church of Scientology Contract for Services
To repeat from the website regarding what makes a contract legal:
A contract must contain consideration: mutual promises to do something or to refrain from something that a party has a legal right to do. Without this mutual promise, there is no valid consideration and the contract is illusory.
(Emphasis added)
No competent lawyer would ever allow their client to sign such a one-sided “contract”. But, of course, Scientologists are not allowed to take the contract to a lawyer. Further, no Scientologist is allowed to have their own copy of the contract.
More from the website:
Look at the relative bargaining power between the parties. A contract will be considered “unconscionable” where there is a gross disparity in bargaining power between the parties and the terms of the contract are oppressive.
Certainly, it is obvious that the terms of Scientology’s contract are quite oppressive. The bargaining power of a Scientologist in this situation is nil. The “Contract for Services” is a take-it-or-leave-it proposition. Sign it or get out. “Bargaining”? Don’t be silly. “Take it to my lawyer”? Not allowed. Require the church to promise to do anything? Definitely not.
All in all, it appears to my non-lawyer eyes that Scientology’s Contract for Services is not valid. There is no quid pro quo – something given or received for something else. Quid pro quo is the essence of a contract. Scientology’s contract is completely one-sided – to the vast benefit to the church and the massive detriment to the Scientologist.
Is this legal?
Ask the Scientologist 
Any contract that is not done on a level playing field, does not have a meeting of minds, contains any level of entrapment, or duress or overwhelm or is constructed or and presented in such way to take advantage of a person’s weakness, disability or ignorance, or contains bait and switch element(s), or has elements of unreasonableness, or contains elements of unconscionability, or where someone who knew what was the underlying (covert) intention or and long term goal of the presenting party, has no force in law and is as if it does not exist.
Quote from the Ontario Consumer protection act:
PART III
UNFAIR PRACTICES
False, misleading or deceptive representation
14 (1) It is an unfair practice for a person to make a false, misleading or deceptive representation. 2002, c. 30, Sched. A, s. 14 (1).
Examples of false, misleading or deceptive representations
(2) Without limiting the generality of what constitutes a false, misleading or deceptive representation, the following are included as false, misleading or deceptive representations:
1. A representation that the goods or services have sponsorship, approval, performance characteristics, accessories, uses, ingredients, benefits or qualities they do not have.
2. A representation that the person who is to supply the goods or services has sponsorship, approval, status, affiliation or connection the person does not have.
3. A representation that the goods or services are of a particular standard, quality, grade, style or model, if they are not.
4. A representation that the goods are new, or unused, if they are not or are reconditioned or reclaimed, but the reasonable use of goods to enable the person to service, prepare, test and deliver the goods does not result in the goods being deemed to be used for the purposes of this paragraph.
5. A representation that the goods have been used to an extent that is materially different from the fact.
6. A representation that the goods or services are available for a reason that does not exist.
7. A representation that the goods or services have been supplied in accordance with a previous representation, if they have not.
8. A representation that the goods or services or any part of them are available or can be delivered or performed when the person making the representation knows or ought to know they are not available or cannot be delivered or performed.
9. A representation that the goods or services or any part of them will be available or can be delivered or performed by a specified time when the person making the representation knows or ought to know they will not be available or cannot be delivered or performed by the specified time.
10. A representation that a service, part, replacement or repair is needed or advisable, if it is not.
11. A representation that a specific price advantage exists, if it does not.
12. A representation that misrepresents the authority of a salesperson, representative, employee or agent to negotiate the final terms of the agreement.
13. A representation that the transaction involves or does not involve rights, remedies or obligations if the representation is false, misleading or deceptive.
14. A representation using exaggeration, innuendo or ambiguity as to a material fact or failing to state a material fact if such use or failure deceives or tends to deceive.
15. A representation that misrepresents the purpose or intent of any solicitation of or any communication with a consumer.
16. A representation that misrepresents the purpose of any charge or proposed charge.
17. A representation that misrepresents or exaggerates the benefits that are likely to flow to a consumer if the consumer helps a person obtain new or potential customers. 2002, c. 30, Sched. A, s. 14 (2).
Unconscionable representation
15 (1) It is an unfair practice to make an unconscionable representation. 2002, c. 30, Sched. A, s. 15 (1).
Same
(2) Without limiting the generality of what may be taken into account in determining whether a representation is unconscionable, there may be taken into account that the person making the representation or the person’s employer or principal knows or ought to know,
(a) that the consumer is not reasonably able to protect his or her interests because of disability, ignorance, illiteracy, inability to understand the language of an agreement or similar factors;
(b) that the price grossly exceeds the price at which similar goods or services are readily available to like consumers;
(c) that the consumer is unable to receive a substantial benefit from the subject-matter of the representation;
(d) that there is no reasonable probability of payment of the obligation in full by the consumer;
(e) that the consumer transaction is excessively one-sided in favour of someone other than the consumer;
(f) that the terms of the consumer transaction are so adverse to the consumer as to be inequitable;
(g) that a statement of opinion is misleading and the consumer is likely to rely on it to his or her detriment; or
(h) that the consumer is being subjected to undue pressure to enter into a consumer transaction. 2002, c. 30, Sched. A, s. 15 (2).
Renegotiation of price
16 It is an unfair practice for a person to use his, her or its custody or control of a consumer’s goods to pressure the consumer into renegotiating the terms of a consumer transaction. 2002, c. 30, Sched. A, s. 16.
Unfair practices prohibited
17 (1) No person shall engage in an unfair practice. 2002, c. 30, Sched. A, s. 17 (1).
Your quote is a bit long. But the important points are simple:
(2)(e) that the consumer transaction is excessively one-sided in favour of someone other than the consumer;
(2)(f) that the terms of the consumer transaction are so adverse to the consumer as to be inequitable;[
I suspect that many countries have similar protection for consumers.
I have not seen any consumer protection laws anywhere in the world, anywhere near as good as the Ontario Consumer Protection Act. If you find any, please let me know.
One might be confused between Scientology’s Contract for Service and Scientologists buying services. They are not directly related.
Buying a service in Scientology is a verbal contract: The church offers a service, a course or some hours of auditing, the Scientologist pays the specified price, the church delivers the course or auditing. That’s a contract with specific offering, an explicit agreement and a paid consideration. That is a separate (and valid) contract.
The written “Contract for Services” is a separate generic “agreement” wherein the church is protected in all ways and offers nothing in exchange for that protection.