Arrest warrants are very specific to date, time of entry, what they can take and look at, and who they can take.  Police warrants are usually issued by the courts, but can also be issued by one of the Chambers of the United States Congress, legislatures and other legal entities.  Here is what to look for when confronted with this situation:

Municipal Court, Springfield Judicial District

To any peace officer of the realm: Complaint upon oath having been brought before me that the crime of larceny has been committed, and accusing Nelson Muntz of the same, you are hereby commanded forthwith to arrest and bring that person before me. Bail may be admitted in the sum of $1,000.00. Dated: 15 May 1997. /s/ Judge Snyder, presiding judge. (example taken from Wikepedia)

Police are required to convince a judge or magistrate that they have ‘probable cause’ and an affidavit that a specific person did do a crime, and if this convinces the judge or magistrate only then will they issue a warrant.  Although the person is not there at the time when the warrant is issued, they can later have a trial against it in court to prove it wrong.

Again, their rights of search are very specific.  So if the warrant reads specifically that there are marijuana plants in the back yard, they are not allowed in the house.  Nor can they search for drugs if the warrant reads they are looking for guns.  However, if they happen to see some other illegal substance or felony charge they  have every right to confiscate and/or deal with it.

There have been cases over the years that were not even warranted to enter a home, sometimes where the Fourth Amendment does not even apply at all.  REMEMBER, the Police have no right to enter you home without your consent, but they are also not obligated to warn you about this.

When it comes to cars, there is no warrant needed.  If a Police Officer believes there may be some contraband or evidence, everything is fair game for their search.

Remember your rights, and to start or for a refresh let us start with the Fourth Amendment:

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.