Appeal from Circuit Court of Champaign County No. 02OV799 Honorable John R. Kennedy, Judge Presiding.
 The opinion of the court was delivered by: Justice Turner
 In June 2002, plaintiff, the City of Champaign (City), filed a complaint against defendant, Christian Torres, alleging he violated article 2, section 23-21(a), of the Champaign Municipal Code, 1985, as amended (Champaign Code) (Champaign Municipal Code, art. 2, §23-21(a) (eff. April 15, 1988)), entitled "[r]esisting or obstructing a peace officer." After an October 2002 bench trial, the trial court found defendant guilty and fined him $175 plus court costs. In November 2002, defendant filed a motion to reconsider, which the court later denied.
 Defendant appeals, asserting the trial court erred in finding him guilty because the peace officer was not engaged in an "authorized act," as required by the ordinance, when the act of resistance occurred. We disagree and affirm.
 At the October 2002 trial, Champaign City police officer Charles Shepard testified that, on April 30, 2002, at about 2:15 a.m., he responded to a report of a loud party at 505 South Fourth Street, Champaign, Illinois, an apartment near the campus of the University of Illinois. Upon arriving, Officer Shepard stood outside the apartment for about 10 minutes, listening to the loud music emanating from the third-floor apartment. He then approached the apartment and knocked on its door three separate times.
 At that point, defendant answered the door, opening it only to the width of his head. Officer Shepard asked defendant if he lived in the apartment, and defendant answered that he did not. The officer then asked defendant to have a resident of the apartment come to the door. Defendant agreed to do so and began to close the door. With his feet planted outside the apartment, Officer Shepard put his right arm on the door and stopped it from being shut. He then instructed defendant to leave the door open "to where it was" and repeated his request to speak with a resident of the apartment. Officer Shepard stated he was not trying to enter the apartment but wanted the door to remain open based on his experience working in the campus area. He explained that, in the past when he had allowed a door to close, the occupants would not open it again, leaving the "problem" unsolved. Defendant told Officer Shepard that he needed to shut the door before he retrieved a resident of the apartment.
 Officer Shepard and defendant argued briefly about the door. At one point, defendant asked Officer Shepard if he had a search warrant, and Shepard responded no, "but [he] was not coming in." Defendant then opened up the door widely, said "'See, there's nothing going on inside,'" and again attempted to shut the door. Officer Shepard put his arm "up against the door to stop it." Defendant again stated he needed to shut the door, opened it widely, and "slammed it very hard against [Officer Shepard's] right arm." Officer Shepard held the door open and informed defendant he was under arrest. The officer then grabbed defendant and pulled him out of the apartment. After a brief struggle, Officer Shepard handcuffed defendant.
 Officer Shepard acknowledged he crossed the threshold of the apartment when defendant struck him with the door and when he grabbed defendant from the apartment.
 Defendant testified on his own behalf. He stated he was a guest at a party and voluntarily opened the apartment door when he heard a knock. Defendant also testified that he showed the officer nothing was going on and went to close the door to where it was originally when Officer Shepard placed himself in front of the door and pulled defendant out.
 At the conclusion of the bench trial, the trial court found defendant guilty of the ordinance violation. In November 2002, defendant filed a motion to reconsider. After a February 2003 hearing, the trial court denied the petition. This appeal followed.
 Article 2, section 23-21(a), of the Champaign Code provides, as follows:
 "No person shall knowingly resist or obstruct the performance by one known to the person to be a peace officer for the City of Champaign of any authorized act within the peace officer's official capacity." Champaign Municipal Code, art. 2, § 23-21(a) (eff. April 15, 1988).
 At issue here is the "authorized act" language, which is also contained in section 31-1(a) of the Criminal Code of 1961 (Criminal Code) (720 ILCS 5/31-1(a) (West 2002) ("Resisting or obstructing a peace officer or correctional institution employee")). Defendant argues the officer's order to keep the door open and his physically keeping the door open were not "authorized acts" because they violated defendant's fourth amendment rights (U.S. Const., amend. IV).
 Neither the Champaign Code nor the Criminal Code defines "authorized," but Illinois courts have defined the term as meaning "'endowed with authority.'" People v. Shinn, 5 Ill. App. 3d 468, 472, 283 N.E.2d 502, 505 (1972), quoting People v. Young, 100 Ill. App. 2d 20, ...