Most newer band definitions specify the limits less in wattage and more in EIRP that measures the actual output of the antenna instead of just the power applied to the antenna by the transmitter. They also specify how the power as to be spread through out the channel and how sharply it has to fall off outside the channel. [0]
[0] See page 3 for an example definition of a VLP definition and requirements from earlier this year. It specifies EIRP and how the power has to be distributed so you're not throwing one big spike in the middle of the channel for example.
> The Further Notice sought comment on the appropriate power levels as well as other rules for VLP devices to ensure that the potential for causing harmful interference to incumbent operations is minimized. (6 GHz Further Notice, 35 FCC Rcd at 3940-42, paras. 236-43.)
