In August 2013 the supervisor of Crater Lake National Park closed the Llao Rock Research Natural Area - including the summit of Llao Rock - except when snow-covered (during winter, when the park roads are closed). When visiting in July 2014 a sign was found indicating the closure on the main trail.

 
Information can be found here: https://www.nps.gov/crla/learn/management/upload/CRLA-Supt-Compendium-Site-Bulletin-2013-2-3.pdf.

Access to the summit may not be possible for some time.

Here's an excerpt from the Supervisor's Compendium:

36 CFR §1.5 – PUBLIC USE LIMITS, CLOSURES: 

The Llao Rock Research Natural Area (RNA) is closed to public entry whenever the area is covered by less than one continuous foot of snow. The Llao Rock RNA is located along the northwest caldera rim and encompasses 435 acres. The closure shall be in effect whenever signs are present designating the closure and when so posted on the park website. This area has recently become a popular hiking destination. Prior to the last decade, Llao Rock received minimal recreational use. The Llao Rock RNA was designated in 1994 to protect rare plant species and preserve whitebark pine (Pinus albicaulis) communities, subalpine pumice and ash fields, and an alpine community mosaic. The increased visitor use has led to damage to sensitive resources which the RNA was designated to preserve and protect. The seasonal closure will ensure that these fragile resources are given the appropriate level of protection and further damage is limited. It will also allow for restoration of areas currently impacted by hiking activity.