Don't think there is a slippery slope when it comes to government restrictions....

Regardless of the merits of phasing out incandescent bulbs....how is this a slippery slope?

As pointed out upthread, the relevant act was adopted in 2007. It's always called for steadily increasing the energy efficiency standards for light bulbs over time, with an eye towards them getting high enough eventually to phase them out over time.

This isn't a case where someone's advocating regulating just X, and then once X is regulated they start regulating Y - which is what people usually mean when they're talking about a slippery slope. If I propose an energy regulation that calls for all incandescent light bulbs to be phased out over the next fifteen years, no one's going to say that this is a "slippery slope" to possibly getting rid of incandescent light bulbs one day. Because that's what the bill actually does! It's not a slippery slope - it's right there in the initial Act! Which is why people have been hoarding incandescent bulbs since at least 2012:

gizmodo.com - The american outlaws hoarding lightbulbs in the name of