Unresolved is what other forms of line-walking might be permitted.

No other form of lighting was permitted - certainly not candles.

Experimental forms of therapy would be permitted only as a final effort to save an embryo's life.

All forms of navigation equipment and communication are permitted.

Two forms of political advertising on the Internet are permitted during election time.

In established States, less serious forms of bad behaviour are also permitted.

Two forms of political advertising on the Internet are permitted during parliamentary elections.

If it is designated as a "scenic" river, some forms of development are permitted.

If one form only is permitted, it is common practice to adopt the plural.

Nevertheless some form of movement was permitted to her.