Tapering lams requires a bit of planning, but after that its easy.
First, build a planer sled with a fence at the back to hold the lam in place.
Then plan a series of shims, varying in thickness from the max you wish to remove to next to nothing. I like to do a shim about every inch for a simple taper like a leg.
Glue the shims in place.
Then set your planer blade height to cut off a wee bit, put in the next leg, repeat as needed, lowering the depth until you are done. Try it on some scrap first to verify your strategy.
Michael Fortune had a nice article about this technique in Fine Woodworking a few years ago.
BTW, the chairs you saw in my dining room had legs made from tapered and bent lams.