The headline of this article from the Yemen Observer says that "reactionary forces" in society are working against women's participation in public life. This quote, though, goes on to elaborate:
“There have been attempts from reactionary forces in the society, the ruling party and opposition parties, to abort the president’s initiative,” Yahya Saleh said at a symposium on Sunday, organized by his forum under the slogan Let’s work together to allocate 15% quota for women.
Reactionary forces in the society plus the ruling party plus the opposition party points to a more deeply ingrained set of prejudices than just reactionary forces alone. Especially given this statement:
The largest opposition party, the Islamist party Islah, still says women can only vote and not run for the posts. It is impermissible for any woman from this party to run.
So it may not be as simple as issuing a presidential decree. Best of luck, though, to all those women who will run in the upcoming (May 17) elections.