Proposed regulations do not become effective until after comments and testimony are received ("notice and comment"), and a final regulation is issued.

Do proposed regulations have the force of law?

Temporary and final regulations have the force of law, while proposed regulations generally do not (except that proposed regulations can be cited as substantial authority for avoiding the understatement of income tax liability under I.R.C. § 6662(b)(2)).

Are proposed regulations authoritative?

Proposed regulations are not considered to be binding until they are finalized. ... During this three year period the regulations are as authoritative as the final regulations.