system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is WalMart able to eliminate medical coverage for part-time employees who've been with the company for years and bypass the Affordable Care Act mandating employers provide healthcare insurance?

From what I gather, WalMart is taking away medical insurance for any employee that averaged less then 30 hours per week for 2013. However, Walmart use to provide medical insurance for part-time employees after a certain period regardless of hours worked per week. Why the change now? Why isn't ACA preventing this?
gpt
Walmart isn't eliminating those prior plans: ACA is.  ACA mandates only certain types of medical insurance, and the old Walmart plans don't qualify.

In terms of why Walmart isn't offering the new ACA-approved plans to part-time employees, it's simply a matter of money.  Those plans cost more money than they're willing to spend on part-time labor.

The reason ACA isn't preventing this is that the authors didn't want to toss part-time workers out of work.  If ACA mandated that part-time workers be provided health care, a large number of them would have simply been laid off to accommodate such a rule.