Batboard

Is licensed transmitter power measured before or after duplexer?

It's going to depend on how the license references the issue.

If it is ERP, it's TX power output minus any filter, duplexer or feedline loss PLUS antenna gain. If it just references transmitter output power, then just measured at the TX port on the radio.

I agree with MSSDave.
MOST EVERY "license" i have seen and assume we are discussing is an FCC license.
If It is I have oly seen "effective radiated power". That being said it can be measured pretty simply.
Go to the antenna , disconnect coax and measure the power out. If you need every watt of TX power the align transmitter while hooked up to your equipment.
Add antenna gain and there 'ya go !