Can a team member(contestant) be added as a reserve member in some other team of the same college for regionals ?

I am a team member of one team of my college. Some other team of my college has only 2 members willing to go to regional if they qualify. They have added the third member just to complete the team. Can I be added as a reserve team member to the their(other) team.

Reserve is not compulsory.

Yeah I know but still if other team adds me as a reserve will it be legal ?