WASHINGTON — On Monday, the Supreme Court:

_Heard arguments over whether employees can sue in federal court over alleged workplace discrimination, despite a collective bargaining agreement between their union and employer requiring that those claims be submitted to binding arbitration.

_Weighed the competing claims of Colorado and Kansas over $9 million in legal fees arising from a dispute over water rights in the Arkansas River.

_Took no action in the case of Ali Al-Marri, who is challenging the president's right to detain him indefinitely and without charge at the Navy brig near Charleston, S.C.

_Refused to enter a politically charged case from West Virginia involving a large punitive damages award against coal giant Massey Energy Co. and allegations of bias by a state judge.

_Declined to block the retrial of celebrity pathologist Cyril Wecht, who is accused of using government workers and equipment to benefit his lucrative private practice.

_Rejected an appeal from a pipeline company over denial of environmental permits for a proposed natural gas pipeline through Long Island Sound.