The extra 2 Europa places are awarded through FA competitions, everyone in English football has the right clinch one of those spots, and it's generally known a couple of months before the season finishes how many league places will be offered entry.
As it stood Spurs could do literally nothing at all to prevent their CL place been taken from them as they weren't in the CL this year. There's also the daft scenario that Chelsea COULD win it again next year and finish outside of the top 4 again.