A number of state and federal laws regulate the use of asterisks and fine print footnotes, including:
 
1. BBB Code of Advertising

An asterisk may be used to impart additional information about a word or term which is not in itself inherently deceptive. The asterisk or other reference symbol should not be used as a means of contradicting or substantially changing the meaning of any advertising statement. Information referenced by asterisks should be clearly and prominently disclosed.

2. Big Print, Little Print

FTC guide for business advertising, includes this advice:

Don’t Bury the Details

Your ads should clearly and conspicuously disclose all the information about an offer that is likely to affect a consumer’s purchasing decision. Disclose the most important information – like the terms affecting the basic cost of the offer – near the advertised price.

Print advertisers should not attempt to hide the real cost or the critical terms or conditions by:

• Putting them in obscure locations, such as the border area on a print ad;
• Burying them in numerous, densely packed lines of fine print; or
• Including them in small-type footnotes.

Television advertisers should not hide key information in:

• A fast moving “crawl”;
• Superscripts or subscripts using small print sizes or a color that fades into the background;
• Type that disappears from the screen too fast for consumers to read and comprehend; or

3. FTC Guide on Use of the Word ‘Free’

“… all of the terms, conditions and obligations should appear in close conjunction with the offer of “Free” merchandise or service. For example, disclosure of the terms of the offer set forth in a footnote of an advertisement to which reference is made by an asterisk or other symbol placed next to the offer, is not regarded as making disclosure at the outset.”  See full guide.

4. Utah automobile advertising law

Disclosure of Material Facts. Disclosures of material facts that are contained in advertisements and that involve types of vehicles and transactions shall be made in a clear and conspicuous manner.

• Factors to be taken into consideration include advertisement layout, headlines, illustrations, type size, contrast, crawl speed and editing.
• Fine print, and mouse print are not acceptable methods of disclosing material facts.
• The disclosure must be made in a typeface and point size comparable to the typeface and point size of the text used throughout the body of the advertisement.
• An asterisk may be used to give additional information about a word or term, however, asterisks or other reference symbols may not be used as a means of contradicting or substantially changing the meaning of any advertising statements.

5. Massachusetts Retail Advertising Regulations

Among the factors to consider in determining if a disclosure is clear and conspicuous: “… [whether] an asterisk or similar symbol is used to denote that a disclosure appears elsewhere in the advertisement, whether every asterisk in the advertisement appears in type which is at least as large as the type size of the disclosure it accompanies, whether the asterisk adjacent to the disclosure is of the same size and appearance as the original asterisk, whether the asterisked information is quickly and easily found and whether the asterisked information gives additional details of a statement rather than changes the meaning of the statement”