Valid and Stringent

adjective

• Well grounded in logic or truth or having legal force.
  • usage: "a valid inference"; "a valid argument"; "a valid contract"
• Still legally acceptable.
  • usage: "the license is still valid"

• (a.) Having sufficient strength or force; founded in truth; capable of being justified, defended or supported; not weak or defective; sound; good; efficacious; as, a valid argument; a valid objection.
• (a.) Having legal strength or force; executed with the proper formalities; incapable of being rightfully overthrown or set aside; as, a valid deed; a valid covenant; a valid instrument of any kind; a valid claim or title; a valid marriage.
• (a.) Strong; powerful; efficient.

Legally binding; authorized.

adjective

• Demanding strict attention to rules and procedures.
  • usage: "rigorous discipline"; "tight security"; "stringent safety measures"
  • synonyms: rigorous, tight

(a.) Binding strongly; making strict requirements; restrictive; rigid; severe; as, stringent rules.