Wyoming on Friday becomes the last state to raise its drinking age to 21, confronting bar owners with a dilemma - what to do about 19- and 20-year-olds who come in legally Thursday night and suddenly become too young to drink after midnight.

The Legislature earlier this year acceded to federal pressure to raise the drinking age from 19 to 21. The increase takes effect at 12:01 a.m. Friday.But state law allows bars to remain open until 2 a.m., and 19-and 20-year-olds expected to turn out in force Thursday night for their last chance for a legal drink.

"It takes effect at 12:01 a.m. July 1 and from that point on, a bar operator cannot sell to or allow someone 19 and 20 to drink in their establishment," said Attorney General Joe Meyer. "So they had better clear the tables."

Complicating the issue is that the law is written in such a way that, unless city ordinances say otherwise, those ages 19 and 20 can still be inside a liquor establishment after the age limit changes.

"It's going to create an unenforceable object," said Police Chief Don Pierson. "It will be totally impossible for us to enforce a law that allows 19- and 20-year-olds in, but doesn't let them drink. The biggest problem is for the bar owner himself, because it is his responsibility to make sure they do not drink."

Bar owners can be fined $35 to $750 and receive up to six months in jail for allowing underage drinking.