The Act Party has suffered more than its share of self-inflicted wounds lately but it deserves credit for a valuable legislative intervention last week. At Act's behest, the Government has agreed to write a clause into the foreshore and seabed bill now before Parliament that will expressly make it unlawful to charge for access to a beach.

The Government was previously content with Attorney- General Chris Finlayson's view that charging would be illegal because the bill would not give iwi any power to do so. Act pressed for a specific prohibition that would leave no room for uncertainty among members of the public and members of tribes awarded customary title.

The wording of the clause has yet to be seen, but if it is simple and clear it should remove at a stroke most people's fear of recognising customary ownership. It will not be sufficient for Act to support the Marine and Coastal Area (Takutai Moana) Bill; the party has a more general objection to the test of customary claims, which is weaker, it believes, than in the Foreshore and Seabed Act the bill will replace. Act also dislikes the idea that iwi will be able to get title from negotiations with the Government rather than going to court.

But it is telling that National has bowed to one of Act's wishes on a bill that Act does not support. The bill can pass on the votes of National and the Maori Party but National clearly does not relish leaving Act with a drum to beat about beach access. Public opinion still needs to be convinced on that point.

The Maori Party is understandably aggrieved at the concession to Act. Co-leader Pita Sharples calls the projected amendment an "insult to the generosity of tangata whenua" who have "consistently said they have no intention of excluding others from the beaches and coasts".

They see the clause as a declaration of distrust of the informal undertakings iwi leaders have given the public ever since the Court of Appeal opened their way to foreshore title. But the principle of public access to beaches is too important to all New Zealanders to be left in the realm of informal assurances or even implicit law.

The law has to be explicit on questions that have the potential to cause conflict at ground level. When beach-goers arrive at a spot that is under customary title both sides need to know clearly what that means. The Act amendments should mean that at least both will know access cannot be refused.

But access for what? Customary title must carry some rights to regulate what can be done on the beach so customary sites, resources and values are respected. Swimming, surfing, sunbathing and boating will surely be safe, fishing and picnicking might not be.

Ironically, a clear prohibition on charges might help gain public acceptance of customary restrictions on beach activities. Nothing discredits cultural values quicker than the offer to waive them for a fee.

If the bill emerges from the select committee with a clause explicitly guaranteeing free access to the foreshore and seabed it will be a fine testimony to coalition government. The bill is the Maori Party's touchstone, the prime purpose of the party's formation and it will probably be its proudest boast at next year's election. But the Government's other partner will be able to boast too.

Both have contributed to a balanced bill that does indeed make it easier for iwi, hapu and whanau to establish customary claims to the coast but should also ensure that the tidal zone remains open to all and free. For that we need simple, clear, black-letter law that will be known to every New Zealander, leaving no room for argument and permitting no barriers to a beach.