You are bound to the limits imposed by your WPS. Especially if it was submitted and customer/engineer approved as is.
Now, that doesn't mean that the code sets that limit. I don't regularly work to ASME and am a little too rushed currently to look it up so hopefully Al or one of the other guys will cover the ASME aspect.
The only way beyond possible code restrictions, which I doubt, is if it is limited because of the notch toughness as Al already mentioned. Depending upon the CVN rating your heat input could be of concern. And, one obvious factor of that is your bead width which affects travel speed which increases/decreases your heat input.
The WPS may have been written to cover many differing scenarios. Just as I often include a maximum Pre-heat/Inter-pass temp of 500-550° so I am covered on Seismic jobs as well as standard D1.1 jobs, they may have restricted the bead width/travel speed to reduce heat input on a large variety of the work that the WPS would be submitted for.
No one will question a WPS with heat input controls, but you may often get questions about a WPS without any.
Have a Great Day, Brent