Bribery Vs. Lobbyist

I have often wondered why it is okay for one person to do something and an other to do quit the same and is punished for his/her efforts.

For example unions get together and collect money from their members which is in turn given to lobbyist to promote the ideals and goals of the union. For example these lobbyist use this money to buy votes and politicians. Of Course this is not how they see it at all. They believe they are making donations to worthwhile causes and charities. These lobbyist have free reign and move in the shadows.

Yet if a private citizen goes and uses their money in the same regard it is a felony. "No Officer I don't want to go to jail. Here is 100.00."

What about the street thug that sells drugs vs. the pharmaceutical company's? Is their really a difference or is the government only regulating our lives.

California Law - Bribery

67. Every person who gives or offers any bribe to any executive officer in this state, with intent to influence him in respect to any act, decision, vote, opinion, or other proceeding as such officer, is punishable by imprisonment in the state prison for two, three or four years, and is disqualified from holding any office in this state.

67.5. (a) Every person who gives or offers as a bribe to any ministerial officer, employee, or appointee of the State of California, county or city therein, or political subdivision thereof, any thing the theft of which would be petty theft is guilty of a misdemeanor.

(b) If the theft of the thing given or offered would be grand theft the offense is a felony.

I have added part of the California Penal Code. Check out the Penal Code and it would see that what these lobbyist are doing is illegal. Can anyone explain to me how this is okay and does this only irritate me?