After federal regional haze standards were adopted in 1999, progress has been minimal. Haze, which includes toxics such as nitrogen oxides, sulfur dioxide, fine particulates, and some volatile organic compounds, impairs visibility and threatens human health and the environment.
Each state (and D.C. and the Virgin Islands) was supposed to finalize a State Implementation Plan (SIP) by 2007, but only two (CA and DE) have met that requirement, leading many environmental groups to initiate additional legal action in January 2011.
On Nov. 9, 2011, EPA signed a consent decree that requires the agency to receive from and approve an SIP for DC, VI, and 43 states that don't have a fully approved one. Most states have already submitted a plan to EPA that the agency says it is reviewing. If EPA doesn't approve all or part of a state's plan, it will develop its own plan for the state's deficient components.
- Visibility, Regulatory Actions  (includes extensive information on prior actions and inactions that preceded the current consent decree); press release. 
The deadlines for EPA to propose and finalize its solution (such as full approval, some type of partial approval, and/or some type of federal plan) for each SIP is as follows (with proposal date first, then final approval date; extensions of up to 60 days are possible under certain circumstances).
- NA/Dec. 13, 2011: NV, OK (remaining unapproved components)
- NA/Dec. 15, 2011: KS, NJ
- NA/March 15, 2012: TN, WV
- Nov. 15, 2011/March 15, 2012: DC, ME
- Nov. 29, 2011/March 29, 2012: SD
- Jan. 17, 2012/May 15, 2012: IL, IN, MN, NY, OH, PA, VA
- Feb. 15, 2012/June 15, 2012: AK, AL, GA, IA, LA, MD, MS, MO, NC, NE, NH, NM (remaining unapproved components), RI, SC, VT, WI
- March 15, 2012/July 13, 2012: CT, MA
- May 14, 2012/Sept. 14, 2012: HI, VI
- May 15, 2012/Nov. 15, 2012: AK, AZ, ID (remaining unapproved components), FL, MI, OK, OR (remaining unapproved components), TX, WA
Each state can determine how it wants to reduce haze. In some cases, the plan will rely on actions already taken, such as reductions in emissions from power plants or vehicles.
Among the environmental groups listed in the consent decree are:
- National Parks Conservation Association. 
- Sierra Club. 
- Environmental Defense Fund. 
- San Juan Citizens Alliance. 
- Powder River Basin Resource Council. 
The consent decree is open for public comment for 30 days after it's published in the Federal Register; search for Docket Number EPA-HG-OGC-2011-929 ).
The five states that aren't included in this consent decree have established timelines for finalizing a plan through consent decrees between WildEarth Guardians (Jeremy Nichols,  303-573-4898 x1303), as well as National Parks Conservation Association and Environmental Defense Fund for the first item below, and EPA.
- Consent decree of Sept. 27, 2011, for CO (proposal due by March 8, 2012/final by Sept. 6, 2012), MT (Jan. 20, 2012/June 29, 2012), ND (was due July 21, 2011/Jan. 26, 2012), and WY (April 15, 2012/Oct. 15, 2012): final consent decree ; more information. 
- Consent decree of Oct. 28, 2010,  for UT (April 30, 2012/Oct. 31, 2012).