Being a female, with children, i can understand the woman's feelings on the fact that she has been with them for 4 years and therefore deserves the tenure.

However, if the law clearly states, 4 years of active continuous employment, then i would say that is pretty well covered and the employer is safe. That is the business HR side speaking.

As to if it is discrimination... i do not think it should be directly related to why she was out. The issue is, how would (has) the rule been applied if she was out 9 months due to a medical condition/trauma? How would (has) the rule been applied to a man who was out due to a heart condition or other such item? The reason for the absence isn't the issue. The issue is, how has the company dealt with employees who were out for whatever reasons in the past? If their refusal of the tenure is constant with all of the cases (and there had to have been someone else with them out for a period of time at some point... ) then it is policy/interpretation of the law and nothing more...

As to men and discrimination. i believe it does happen at times. i live in the states and when my youngest was born my husband asked for 2 weeks off to help with the twins and the new baby. A lady at the office, who had just given birth was out for 6 weeks paid, but he was told that he couldn't take the 2 weeks (paid or unpaid) unless he took vacation/leave time. THAT in my mind was discrimination... personal opinion.