This drinking party happened in the episode "Arrested".
Haley was at this party with many other people and they happened to be drinking.
Suddenly, just after 2 in the morning cops busted the party and everyone attempted to escape. Students ran off, while Haley started climbing down a fire escape and ended up falling on top of a police officer. Another cop came and told Haley not to move and she cried out "Don't hurt me! I'm just a student! I'm Haley Dunphy!". Haley was then arrested and taken to jail. It is unknown what happened to the other party participants, if they were students at Haley's college and underage and if any of them got arrested with Haley.
Just after 3 in the morning, almost an hour after the party was busted, the news of Haley's arrest reached her parents Phil and Claire who immediately got dressed to go and bail her out and brought Mitchell, the family lawyer who is Haley's uncle and Claire's brother. Mitchell's boyfriend Cameron, their daughter Lily and also Claire and Mitchell's father Jay and stepmother Gloria, as well as Haley's sister Alex and brother Luke were also told of this, but whether anyone told Claire and Mitchell's stepbrother Manny and the former two's mother Dede about Haley's arrest is unknown.
After Haley was bailed out, she had to attend a disciplinary hearing and instead of defending herself, she blurted out everything illegal she had done since the day she started college.
After the hearing, Haley was expelled from college and she returned home.