Student culture, from the alcohol-fuelled exuberance of orientation to on-campus clubs, might be curtailed if legislation allowing students to choose not to join students' associations is passed.

Student services, including welfare and advocacy, might also be affected, forcing universities themselves to pick up the tab at a time when they are facing considerable financial pressure.

Parliament's education and science committee is hearing submissions on the Education (Freedom of Association) Amendment Bill which would let tertiary students decide for themselves whether to join a student union.

The bill's sponsor, Act list MP Sir Roger Douglas, argues that student unions are the only remaining area where the right to free association isn't respected.

Individuals should be free to associate with any group they choose, he reasons, and the current law around students' associations does not allow this choice.

Labour and the Green Party oppose the bill, since a significant number of past and present caucus members got their start in politics at that level.

National's coalition partner, the Maori Party, has also opposed it, citing support from students' associations for issues such as the African American civil rights movement and the hikoi opposing the Foreshore and Seabed Bill five years ago.

But the bill's likely effect on its key political adversary must surely make Sir Roger's measure appealing to National, which supported it at its first reading.

National supported a similar private member's bill from one of its own MPs in the late 1990s that was eventually softened.

National is arguably in a stronger political position this time around. Should it choose not to support the legislation all the way, it is likely to face questions from supporters, particularly the Young Nationals, about its commitment to its core values.

Although the official line from Tertiary Education Minister Steven Joyce and National MPs is that caucus will wait to see the report from the select committee before making a decision, the signs point to National backing the bill.

That may mean big changes for students and universities.

The NZ Union of Students' Associations opposes the bill because a voluntary regime would virtually guarantee its members a plunge in membership and a dramatic fall in income.

That would lead to a reduction in services to students, including welfare and advocacy, representation, recreation and leisure, entertainment and social activities, and media and publications.

The NZUSA values those services at about $25 million a year.

It points to Australia, where association fee income fell 95 per cent after membership was made voluntary in 2007, forcing the Government to provide "transitional support" - to the tune of $120 million, according to the NZUSA - to maintain key services.

Association membership at Auckland University, whose students opted for voluntary membership in 1999, went from about 33,000 members to just 3000 and only recovered to above 20,000 once the nominal membership fee was waived.