Here is what Title 36, Section 176 of the US Code says about this topic:


Sec. 176. Respect for flag

Statute

No disrespect should be shown to the flag of the United States of America;
the flag should not be dipped to any person or thing.

(b) The flag should never touch anything beneath it, such as the ground,
the floor, water, or merchandise.

(k) The flag, when it is in such condition that it is no longer a fitting
emblem for display, should be destroyed in a dignified way, preferably by
burning.


-CITE-

36 USC CHAPTER 10 - PATRIOTIC CUSTOMS 01/16/96

-EXPCITE-

TITLE 36 - PATRIOTIC SOCIETIES AND OBSERVANCES
CHAPTER 10 - PATRIOTIC CUSTOMS
.

Links to the U.S. House of Representatives Internet Law Library Home Page

-CITE-

4 USC CHAPTER 1 - THE FLAG 01/02/01

-EXPCITE-

TITLE 4 - FLAG AND SEAL, SEAT OF GOVERNMENT, AND THE STATES
CHAPTER 1 - THE FLAG
.

-HEAD-


CHAPTER 1 - THE FLAG

-MISC1-


Sec.

bullet1. Flag; stripes and stars on.
bullet2. Same; additional stars.
bullet3. Use of flag for advertising purposes; mutilation of flag.
bullet4. Pledge of allegiance to the flag; manner of delivery.
bullet5. Display and use of flag by civilians; codification of rules and customs; definition.
bullet6. Time and occasions for display.
bullet7. Position and manner of display.
bullet8. Respect for flag.
bullet9. Conduct during hoisting, lowering or passing of flag.
bullet10. Modification of rules and customs by President.