Opposite direction separation is locally directived. At my base it used to be IFR/IFR-6 miles, either A/C VFR-3 miles, but was recently changed to IFR/IFR-10 mi, either A/C VFR-6 mi due to too many close calls. I actually got busted on my rating day for opposite direction separation bust, but it was 9 1/2 miles separation and this was 2 days after they changed the rules (I didn't even know they had changed the rule). So I still got my rating cuz the rest of the day was exceptional for me.